Artificial lighting systems for closed environments often aim at improving the visual comfort experienced by users. In particular, lighting systems are known which imitate natural lighting, specifically sunlight illumination, in particular using light with a high correlated color temperature (CCT), and a large color rendering index (CRI). The characteristics of such a to be imitated outdoor lighting depend on the interaction between the sunlight and the earth atmosphere and create a specific shade characteristic.
EP 2 304 478 A1, EP 2 304 480 A1, PCT/IB2013/060141 filed on 14 Nov. 2013 as well as PCT/EP2014/000835 filed on 27 Mar. 2014, all filed by the same applicant, disclose lighting systems with a light source producing visible light, and a panel containing nanoparticles. During operation of the lighting system, the panel receives the light from the light source and acts as a so-called Rayleigh diffuser, namely it diffuses light rays similarly to the earth atmosphere in clear-sky conditions. Specifically, the concept uses directed light, which corresponds to sunlight and generates shadows in presence of lit objects, and diffused light with a larger CCT, which corresponds to the light of the blue sky.
For providing cool white light as well as warm white light, LED based light sources may be used that are based on, for example, phosphor-converted white LEDs and/or a combination of various color LEDs. The optical properties of light emitted from LEDs require beam shaping optical configurations, usually collimating optics such as lens and/or mirror systems.
The present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.